Many satellites and other spacecraft, as well as some terrestrial stationary and vehicle applications, such as seagoing vessels, can include one or more energy storage flywheel systems to provide both a backup power source and to provide attitude control for the vehicle. In such systems, each flywheel system is controlled and regulated to balance the electrical demand in the vehicle electrical distribution system, and may also be controlled in response to programmed or remote attitude (or torque) commands received by a main controller in the vehicle.
Many energy storage flywheel systems include one or more components that are rotationally supported within a housing assembly. These components, which may be referred to as the rotating group, include, for example, an energy storage flywheel, a motor/generator, and a shaft. In particular, the energy storage flywheel and motor/generator may be mounted on the shaft, which may in turn be rotationally supported in the housing assembly via one or more bearing assemblies. In many instances, the shaft is rotationally supported using one or more primary bearing assemblies, and one or more secondary, or back-up, bearing assemblies. For example, in many satellite and spacecraft applications, the flywheel system may include one or more magnetic bearing assemblies that function as the primary bearing assemblies, and one or more mechanical bearing assemblies that function as the secondary bearing assemblies. Typically, the primary bearing assemblies are used to rotationally support the rotating group, while the secondary bearing assemblies are otherwise disengaged from the rotating group. If one or more of the primary bearing assemblies is deactivated due, for example, to a malfunction, or otherwise becomes inoperable to rotationally support the rotating group, the secondary bearing assemblies will then engage, and thereby rotationally support, the rotating group.
In some systems, the secondary bearing assemblies are fixedly mounted and, upon deactivation of the primary bearing assemblies, the shaft is brought into contact with the secondary bearing assemblies. While safe and generally effective, this configuration can cause damage to either or both the shaft and secondary bearing assemblies if the shaft is rotating at a relatively high speed when the primary bearing assemblies are deactivated.
In other systems, the secondary bearing assemblies are spring loaded, or otherwise biased, toward either the engaged or disengaged position. If the secondary bearing assemblies are spring loaded toward the disengaged position, then in order to move the secondary bearing assemblies to the engaged position, an actuator may be energized to overcome the spring load and move the bearing assemblies to the engaged position. Conversely, if the secondary bearing assemblies are spring loaded toward the engaged position, then in order to move the secondary bearing assemblies to the disengaged position, an actuator may be energized to overcome the spring load and move the bearing assemblies to the disengaged position. In either of these instances, the actuator may be configured to rapidly move the secondary bearing assemblies into contact with the shaft. This configuration, too, can cause damage to the shaft and/or secondary bearing assemblies if the shaft is rotating at a relatively high speed when the primary bearing assemblies are deactivated.
Hence, there is a need for an auxiliary, or secondary, bearing assembly system that improves on one or more of the above-noted drawbacks. Namely, a bearing assembly system that substantially eliminates, or at least lessens the likelihood of, damage occurring to the shaft and/or secondary bearing assemblies when the secondary bearing assemblies are engaged while the shaft is rotating at relatively high speeds. The present invention addresses one or more of these needs.